probablepeople.RepeatedLabelError for 'Captain Don Shackelford'

[vaudric]

Raise RepeatedLabelError(raw_string, parse(raw_string), label)
probablepeople.RepeatedLabelError:
ERROR: Unable to tag this string because more than one area of the string has the same label

ORIGINAL STRING: Captain Don Shackelford
PARSED TOKENS: [('Captain', 'Surname'), ('Don', 'GivenName'), ('Shackelford', 'Surname')]
UNCERTAIN LABEL: Surname

When this error is raised, it's likely that either (1) the string is not a valid person/corporation name or (2) some tokens were labeled incorrectly